In the United States, pet cats outnumber pet dogs, yet our understanding and treatment of pain in cats has lagged behind that in dogs. Veterinarians consider surgical procedures in dogs and cats to be equally painful, but we treat cats perioperatively for pain less often than we do dogs.1 This undertreatment of pain results, in part, from the difficulty in recognizing and assessing pain in cats.

Various pain-scoring systems have been used to assess postoperative pain. These systems measure physiologic data (objective) or evaluate behavior (subjective) or do both. Algometers and pressure platform gait analysis are objective pain measuring tools, whereas the visual analog scale (VAS) is an example of a widely used subjective scoring system. The basic VAS used for assessing pain consists of a continuous line anchored at either end with a description of the scale's limits. For example, "no pain" would be at one end of the scale and "severe pain" would be at the other. The observer places a mark on the line that he or she thinks correlates to the animal's degree of pain. This mark is later converted to a number by measuring the distance of the mark from zero.

Each practice should choose or design a scoring system that meets its own specific needs; finding this system may require some trial and error. The system chosen should be user-friendly for veterinarians and support staff. It should also be an integral part of an animal's postoperative evaluation. That is, after checking temperature, pulse, and respiration, you should assess the patient for pain—the fourth vital sign.

The scale you choose should include both noninteractive and interactive components and should rely heavily on changes in behavior. For example, with the dynamic and interactive visual analog scale (DIVAS)—an extension of the VAS—animals are first observed undisturbed from a distance and are then approached, handled, and encouraged to walk or move around. Finally, the surgical incision and surrounding area are palpated, and an overall assessment of pain is made.

BEHAVIORS CORRELATED WITH PAIN

To assess postoperative pain, evaluate a cat's posture and orientation and position in the cage, facial expression, loss of normal behaviors, and response to palpation.

Posture

1. After surgery, this cat's posture—hunched with a lowered head—indicates pain.

A cat that adopts a hunched posture with its head hung low, sits quietly and seeks no attention, or resents being handled is likely experiencing pain (Figure 1). In one of the few studies in which detailed behavioral ethograms (quantitative descriptions of animal behavior) have been constructed, a hunched or tucked up posture appears to be correlated with acute pain in cats after abdominal surgery.2 This observation has been corroborated by preliminary work at the University of Glasgow (Robertson SA, College of Veterinary Medicine, University of Florida. Unpublished data, 2007).

Orientation in cage

A cat experiencing postoperative pain will often sit in the back of its cage. This subtle sign of pain will remain unrecognized if the caregiver expects to see more active signs of pain, such as pacing, agitation, or vocalizing.

Facial expression

2. This cat's posture and facial expression are consistent with abdominal pain.

A head-down posture, with eyelids half-closed and eyes held in a slanted position may correlate with pain (Figure 2).